The present invention relates to a new and improved group control for elevators containing an apparatus for controlling the descent peak down-peak traffic, by means of which a defined number of descent or down storey or hall calls is allocated to each cabin in the elevator group.
Group controls containing such apparatus serve the purpose of controlling the elevators of the group in the event of extreme collective traffic in the direction of the ground floor or any other primary stop or landing which, for example, may occur in an office building with unstaggered office closing or quiting times or at the end of visiting hours in hospitals. By means of the group control short and balanced waiting periods or times or intervals are intended to be realized for the passengers. The apparatus may be activated either by means of a timer switch or by means of a measuring device determining the flow of traffic in the direction of the primary stop or landing of the building. Simultaneously, the servicing of ascent or up calls may be reduced or totally eliminated.
In a state-of-the-art group control as known, for example, from German Patent Publication No. 1,803,648 the storeys or floors are divided into groups of fixed zones. The elevator system switches to the descent peak or down-peak operation or mode when a predetermined number of descent or down calls is exceeded in more than one zone or when a descending elevator cabin or car is fully occupied. During that operational mode an allocation device compares the number of registered descent or down calls with the number of cabins or cars used to answer the same. When the ratio of the two numbers exceeds a predetermined value a further cabin or car is incorporated into the servicing operation.
The control now operates in such a manner that a first cabin or car which, for example, is allocated to descent or down calls in an upper zone travels to the call originating from the highest storey or floor in this zone, while a second cabin or car which is also allocated to this zone answers or services the highest descent or down call in a lower section of the same zone. When the first cabin or car is allocated to the upper zone it is also excluded from the descent peak traffic. When descent or down calls are simultaneously present in a lower zone, the second cabin or car will be allocated to the lower zone and answers or services the call from the highest storey or floor in this zone even though the number of predetermined descent or down calls in the upper zone may be exceeded. In this manner an alternating preferred servicing of the zones and balanced waiting periods or times are intended to be achieved.
It is comtemplated with this control system to allocate only a predetermined number of descent or down calls to be serviced by each cabin or a car for achieving minimum waiting periods or times by fixing this predetermined number, and thus, the entering stops for each cabin or car as well as by alternating preferred servicing of the zones. However, it will be evident from the foregoing that the predetermined number of entering stops of a cabin or car may be considerably exceeded in certain cases, so that minimum waiting periods or times can hardly be achieved. A further disadvantage is that cabins or cars which are fully occupied by having answered or serviced descent or down calls of the upper zone sections no longer can service descent or down calls present in the lower zone sections, so that additional means have to be employed to eliminate this disadvantage.
One difficulty in the conception of such controls arises with regard to the determination of the optimum number of entering stops per cabin or car. Since some uncertainties exist in this respect, a small number like for example, two is used in practice, and there is accepted the fact that this number may be possibly considerably exceeded.